Descending and non-descending tornadic vortex signatures
detected by WSR-88Ds
R. J. TRAPP, E. D. MITCHELL
National Severe Storms Laboratory, NOAA
and
Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma
Norman, Oklahoma
G. A. TIPTON, D. A. EFFERTZ
National Weather Service, NOAA
Chanhassen, Minnesota
A. I. WATSON
National Weather Service, NOAA
Tallahassee, Florida
D. L. ANDRA
National Weather Service, NOAA
Norman, Oklahoma
M. A. MAGSIG
NEXRAD Operational Support Facility/Operations Training Branch, NOAA
Norman, Oklahoma
Jeff Trapp
NSSL/CIMMS
1313 Halley Circle
Norman, OK 73069
PH (405)366-0512, FAX (405)366-0472
Jeff.Trapp@nssl.noaa.gov
Tornadic vortex signatures (TVSs) of 52 tornadoes were identified and analyzed,
then characterized as either "descending" or "non-descending." This characterization refers
to a known tendency of radar-observed tornadic vortices, namely, that of their formation
aloft and subsequent descent leading to tornadogenesis. Only 52% of the sampled TVSs
descended according to this archetypal model. The remaining 48% tended to form either
near the ground and grow upward or form nearly simultaneously over a several kilometer
depth. Theoretical explanations have been offered elsewhere for these two primary modes
of tornado development. The result was stratified according to attributes of the tornado and
TVS. For example, tornadoes within squall lines tended to be associated with
non-descending TVSs, identification of which provided a mean tornado lead time of 5 min.